Method and device for producing grooved bolts

ABSTRACT

The invention relates to a method for producing a bolt ( 10 ) with a head ( 12 ) which is provided with a circumferential groove ( 20 ) or channel, wherein the groove ( 20 ) or channel is produced by pressing a bulge ( 18 ) against the head ( 12 ) by means of a radially active closing tool ( 112 ).

TECHNICAL FIELD

The present invention relates to a method and a device for producing bolts having a head which is provided with a peripheral groove or channel (grooved bolts), and a device suitable for this.

Corresponding grooved bolts act, for example, as a basis for stabiliser ball pins and comprise a cylindrical shaft and a cylindrical head, which has a horizontally extending groove or channel.

PRIOR ART

Previously, these grooved bolts were provided with the desired groove by means of a cutting processing operation, that is to say, by means of turning. A complex additional operating step was thereby required, additional cutting waste occurred and the strength of the turned groove or channel was not optimum.

SUMMARY OF THE INVENTION

Based on this prior art, an object of the present invention is therefore to provide a method and a device for producing such a grooved bolt, in which no additional operating steps are required, the material use and the material waste are reduced and better strength can be achieved.

According to the invention, the above object is achieved with a method for producing a bolt having a head which is provided with a peripheral groove or channel, wherein the groove or channel is produced in a non-cutting manner by pressing a bead on the head of the bolt using a radially active closure tool.

It is particularly preferable for the bolt to be produced from a wire portion by twice pre-compressing the head and final compression, with the bead for the groove or the channel being produced. In this manner, according to the invention a bolt having a groove can be produced during the same operating steps as were previously necessary for the bolt blank which was intended to be processed by means of a cutting processing operation, that is to say, by means of turning. According to the invention, an entire operating step can thus be saved on an additional processing machine (turning machine).

It is particularly preferable for the head of the bolt, during pre-compression, to assume the shape of two concentric cylinders which are located one on top of the other, the shaft-side cylinder having a larger diameter than the cylinder arranged thereabove and, during final compression, for there to be produced on the upper end of the upper cylinder a radially outwardly extending bead which then forms the upper delimitation of the groove or channel by the two concentric cylinders being surrounded by jaws of a tool which are provided with corresponding steps during the final compression operation so that only the uppermost end of the uppermost cylinder can be deformed outwards during the final compression operation.

It is particularly preferable for the tool for final compression to be provided with a socket which has a cylindrical opening in which a cupping insert for receiving the shaft of the precompressed bolt in the axial direction of the opening is movably arranged and which widens upwards in a conical manner and in which there are moved downwards in an axial direction during the final compression operation the jaws of the tool which have at the outer sides thereof chamfered portions which correspond to the conical widening so that they automatically close around the head of the bolt during the final compression operation.

Finally, it is further particularly preferable for the stamp which is required for final compression of the head of the bolt and for producing the bead to be constructed in a hollow-cylindrical manner and to be received in a hollow-cylindrical stamp retention member in an axially displaceable manner and for the stamp retention member to be designed in such a manner that it first presses the jaws of the tool downwards during the final compression operation so that they close around the head of the bolt and the stamp is only then moved downwards in order to form the bead as an upper delimitation of the groove or channel.

Finally, an object of the present invention is also achieved with a device for producing a groove or channel on the head of a bolt in a non-cutting manner, in which the device comprises jaws which are provided with corresponding steps and which engage around the head of the bolt during the final compression operation.

It is particularly preferable for the device to be provided with a socket which has a cylindrical opening in which a cupping insert for receiving the shaft of the pre-compressed bolt in the axial direction of the opening is movably arranged and which widens upwards in a conical manner and in which there can be moved downwards during the final compression operation the jaws which have at the outer sides thereof chamfered portions which correspond to the conical widening and by means of which they can automatically close around the head of the bolt during the final compression operation.

It is further preferable for the device to comprise a hollow-cylindrical stamp which is received in a hollow-cylindrical stamp retention member in an axially displaceable manner, the stamp retention member being arranged in such a manner that it first presses the jaws downwards during the final compression operation so that they close around the head of the bolt and the stamp can only then be moved downwards in order to form the bead as an upper delimitation of the groove.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS

The present invention is explained in greater detail below with reference to the embodiment illustrated in the drawings, in which:

FIG. 1 shows a pressing blank for a grooved bolt according to the invention;

FIG. 2 shows the completed grooved bolt according to the present invention;

FIG. 3 shows the tool according to the invention for producing a grooved bolt according to FIG. 2 from a pressing blank according to FIG. 1 in the open state sectioned along the axis of rotation;

FIG. 4 shows the tool of FIG. 3 in the open state viewed from above (from the operating direction of the stamp);

FIG. 5 shows the tool from FIG. 3 in the closed state with the grooved bolt inserted at the end of the forming of the bead, also sectioned along the axis of rotation; and

FIG. 6 shows the tool of FIG. 5 in the closed state viewed from above (without a bolt blank and without a pressing stamp).

BEST WAY OF CARRYING OUT THE INVENTION

FIG. 1 shows a conventional pressing blank 10′ for a grooved bolt 10 according to the invention. From a similar pressing blank 10′ but with a larger volume, a grooved bolt which corresponded to FIG. 2 was previously produced according to the prior art by turning a groove in the head 12′.

FIG. 2 shows the grooved bolt 10 produced from the pressing blank 10′ according to the invention by means of pressing, that is to say, exclusively by means of non-cutting processing operations. It comprises a shaft 11, which is adjoined by a head 12 which comprises two concentric cylindrical portions 14 and 16 which are arranged one above the other, the cylindrical portion 16 located further away from the shaft having a smaller diameter and forming together with the bead 18 located even further away from the shaft the groove or channel 20.

According to the invention, the grooved bolt 10 is produced from the pressing blank 10′ in that a special tool, which is explained in greater detail below, engages around the cylindrical portions 14 and 16 of the head 12 and consequently by means of a hollow-cylindrical stamp there is applied to the uppermost portion of the head 12 a pressing action by means of which the bead 18 is formed. The precise production operation is explained in greater detail below with reference to the description of the special tool which is provided for this purpose according to the invention. This special tool is a device for non-cutting production of a groove or channel on the head of a pressing blank 10′ of a bolt.

FIG. 3 shows the lower portion of the tool 100 in the open state, without a pressing blank being inserted. The tool 100 is rotationally symmetrical and illustrated in FIG. 3 in a state sectioned along the rotation axis thereof. The tool 100 according to the invention illustrated in FIG. 3 for non-cutting production of a groove or channel on the head of a bolt has a hollow-cylindrical socket 102 which centrally has a concentric cylindrical opening 104 which widens upwards in a conical manner. In the opening 104, a cupping insert 106 which is also hollow-cylindrical is arranged coaxially with respect to the socket 102 so as to be able to be displaced along the common rotation axis. An ejector pin 108 is also concentrically arranged inside the cupping insert 106. In the open state, the cupping insert 106 protrudes upwards into the region 110 of the opening 104 that widens in a conical manner. Above the cupping insert 106, the individual jaws 112 of the segmented tool can be seen. In this instance, an embodiment with four such segments 112 is illustrated. Naturally, the present invention may also be produced with three, five, six or more such segments. The individual segments are designed in the form of a circle sector and have at the inner side thereof two steps 114, 116 which in the closed state abut the respective steps 14, 16 of the head 12 of the bolt 10 and delimit a deformation of this region of the head during the pressing operation, in order to ensure dimensional accuracy within the required specifications and provisions. At the outer side, the jaws 112 are chamfered in a conical manner at the same angle as the conical region 110 of the opening 104. In this manner, the jaws 112, when they are moved downwards during the pressing operation, are automatically closed since they are necessarily brought together by the inclined portions 110 of the opening 104.

In this state, a pressing blank 10′ can be inserted with the shaft 11′ thereof into the cylindrical opening 118 of the cupping insert 106. How the further final compression operation (pressing operation) is carried out will be explained below with reference to FIGS. 5 and 6.

FIG. 4 shows the device 100 of FIG. 3 from above. The four jaws 112 which are opened and which therefore have corresponding slots therebetween and the socket 102 which surrounds them can be seen clearly. In the centre, it is possible to see the opening for receiving the shaft 11′ of the pressing blank 10′, which is closed at the lower end thereof by means of the ejector pin 108.

FIG. 5 shows the actual closing pressing operation of the final compression operation of a grooved bolt 10 produced according to the invention. The grooved bolt 10 is inserted into the opening 118 of the cupping insert 106 so that the head 12 of the bolt 10 protrudes beyond the cupping insert 106.

The pressing operation of the final compression operation is brought about by an upper tool part 120. This comprises a hollow-cylindrical stamp 122, which is concentrically surrounded by a stamp retention member 124, the stamp retention member 124 also being designed in a hollow-cylindrical manner and both members being arranged concentrically. The stamp 122 is movably inserted in the stamp retention member 124 parallel with the common rotation axis. The stamp 122 is itself constructed in a hollow manner and has a concentric cylindrical opening, whose inner diameter is slightly smaller than the protuberance of the head 12′ of the bolt blank 10′ which extends beyond the two cylindrical steps 14 and 16 of the bolt 10. Furthermore, there moves in this opening of the stamp 122 another ejector pin 126 which can also be moved parallel with the common rotation axis.

In FIG. 5, in comparison with FIG. 3, the operation of final compression of the head 12 of the bolt 10 can be seen clearly. The upper tool part 120 is lowered onto the lower tool 100. The stamp retention member 124 thereby first comes into abutment with the jaws 112 and subsequently pushes them downwards so that they are necessarily pushed together by the conical inclined portions 110 of the opening 104 until they securely surround the two cylindrical portions 14, 16 of the head 12 of the bolt 10. Subsequently, the stamp 122 is moved further downwards so that it pushes a portion of the upper protuberance of the head 12′ of the blank 10′ downwards and radially outwards so that the bead 18 is thereby produced. At the same time, a dimensionally precise pressing operation within the required specifications and provisions of the two cylindrical portions 14 and 16 of the head 12 of the bolt 10 is ensured by the jaws 112. In this manner, the groove or channel 20 on the head 12 of the bolt 10 is produced in a single pressing operation.

Owing to the machine-related backward movement, the upper tool part 120 which comprises the components 122/124/126 and which holds down the head 12 of the bolt 10 is lifted again from the completely pressed head 12 of the bolt 10. The jaws 112 can then open again and the completed bolt 10 can be ejected from the opening 118 in the cupping insert 106 by the ejector pin 108.

During the construction of the device according to the invention, it should be taken into account that the outer periphery of the stamp retention member 124 must be adapted in terms of diameter and inclination to the conical region 110 of the opening 104 in the socket 102. It must therefore have a smaller outer diameter and an inclined portion which is smaller than or equal to the conical region 110.

FIG. 6 shows the tool 100 from above with closed jaws 112. The bolt 10 and tool upper part 120 are not illustrated in this instance.

It can clearly be seen how the jaws 112 have closed by being lowered into the conically chamfered region 110 of the opening 104 (in particular in comparison with FIG. 4).

Using the present invention, a corresponding grooved bolt can be produced in a significantly more rapid and efficient manner, and without the production of cutting waste. Furthermore, the bolt head has better strength values owing to the non-cutting production. 

1. Method for producing a bolt (10) having a head (12), which is provided with a peripheral groove (20) or channel, characterised in that the groove (20) or channel is produced by pressing a bead (18) on the head (12) using a radially active closure tool (112).
 2. Method according to claim 1, characterised in that the bolt (10) is produced from a wire portion by twice pre-compressing the head (12) and final compression, with the bead (18) for the groove (20) being produced.
 3. Method according to claim 2, characterised in that, during pre-compression, the head (12) of the bolt (10) assumes the shape of two concentric cylinders (14, 16) which are located one on top of the other, the shaft-side cylinder (14) having a larger diameter than the cylinder (16) arranged thereabove, and in that, during final compression, there is produced on the upper end of the upper cylinder (16) a radially outwardly extending bead (18) which then forms the upper delimitation of the groove (20) or channel by the two concentric cylinders (14, 16) being surrounded by jaws (112) of a tool (100) which are provided with corresponding steps (114, 116) during the final compression operation so that only the uppermost end of the uppermost cylinder (16) can be deformed outwards during the final compression operation.
 4. Method according to claim 3, characterised in that the tool (100) for final compression is provided with a socket (102) which has a cylindrical opening (104) in which a cupping insert (106) for receiving the shaft (11′) of the precompressed bolt (10′) in the axial direction of the opening (104) is movably arranged and which widens upwards in a conical manner and in which there are moved downwards in an axial direction during the final compression operation the jaws (112) of the tool (100) which have at the outer sides thereof chamfered portions which correspond to the conical widening (110) so that they automatically close around the head (12) of the bolt (10) during the final compression operation.
 5. Method according to claim 4, characterised in that the stamp (122) which is required for final compression of the head (12) of the bolt (10) and for producing the bead (18) is designed in a hollow-cylindrical manner and is received in a hollow-cylindrical stamp retention member (124) in an axially displaceable manner and the stamp retention member (124) is designed in such a manner that it first presses the jaws (112) of the tool (100) downwards during the final compression operation so that they close around the head (12) of the bolt (10) and the stamp (122) is only then moved downwards in order to form the bead (18) as an upper delimitation of the groove (20).
 6. Device (100) for producing a groove (20) or channel on the head (12) of a bolt (10) in a non-cutting manner, characterised in that the device (100) comprises jaws (112) which are provided with corresponding steps (114, 116) and which engage around the head (12) of the bolt (10) during the final compression operation.
 7. Device (100) according to claim 6, characterised in that it is provided with a socket (102) which has a cylindrical opening (104) in which a cupping insert (106) for receiving the shaft (11′) of the pre-compressed bolt (10′) in the axial direction of the opening (104) is movably arranged and which widens upwards in a conical manner and in which there can be moved upwards after the final compression operation the jaws (112) which have at the outer sides thereof chamfered portions which correspond to the conical widening (110) and by means of which they can automatically close around the head (12) of the bolt (10) during the final compression operation owing to the downward movement.
 8. Device (100) according to claim 7, characterised in that it comprises a hollow-cylindrical stamp (122) which is received in a hollow-cylindrical stamp retention member (124) in an axially displaceable manner, the stamp retention member (122) being arranged in such a manner that it first presses the jaws (112) downwards during the final compression operation so that they close around the head (12) of the bolt (10) and the stamp (122) can only then be moved downwards in order to form the bead (18) as an upper delimitation of the groove (20) or channel. 